CN105016555A - Garbage fly ash water washing liquid evaporation desalination system and method - Google Patents

Abstract

The invention discloses a system and method for evaporative desalination of garbage fly ash water washing liquid. The system divides evaporative concentration and evaporative crystallization into two relatively independent units, and the required heat energy is provided and maintained by a compressor system; the evaporative concentration unit Including preheater, falling film evaporator and falling film separator, through preheating and repeated evaporation of garbage fly ash washing liquid, the material is concentrated; evaporation and crystallization unit includes forced circulation separator, forced circulation evaporator, concentrated material passes through After further evaporating, the material reaches a saturated or supersaturated state, and crystallized salt begins to precipitate; the present invention subsequently sets up a thickener and a centrifuge, and after the thickener settles and concentrates and the centrifuge separates, the salt in the garbage fly ash washing liquid can be recovered. eventually separated. The above-mentioned system adapts to the characteristics of complex components of garbage fly ash washing liquid and high salt concentration, and has the characteristics of large evaporation capacity, stable operation and smooth desalination, thus ensuring large-scale and stable disposal of garbage fly ash washing liquid.

Description

A system and method for evaporative desalination of garbage fly ash washing liquid

technical field

The invention relates to the technical field of evaporative desalination, and is especially suitable for evaporative desalination of salty water with complex components and high concentration. Specifically, it relates to an evaporative desalination system and method for garbage fly ash washing liquid.

technical background

Garbage fly ash refers to the residue collected from the flue gas purification system of waste incineration power plants. It contains organic pollutants such as dioxins and furans and soluble heavy metals such as Pb and Cr. Effective disposal. According to the composition characteristics of waste fly ash, sintering cement as raw material is an effective method to dispose of waste fly ash, but the content of chloride ion in waste fly ash is high, and directly used as cement raw material will cause skinning and blockage, which will affect the normal operation of cement kiln. Therefore, it is necessary to pretreat the fly ash of garbage.

Many studies and experiments have shown that water washing is an effective pretreatment method. After the waste fly ash is pretreated by water washing, the chloride ion content is greatly reduced, which is suitable for subsequent cement kiln disposal. Containing a higher concentration of chlorine salt requires evaporative desalination. The Chinese invention patent with the patent number ZL201110031075.2 "A system and method for extracting potassium and sodium salts from garbage incineration fly ash" discloses a unit for extracting potassium and sodium salts from garbage fly ash washing liquid, which mainly includes preheating device, evaporator, flash crystallizer and steam mechanical compressor, etc. This unit is actually a very simple MVR (Mechanical Vapor Recompression) system. Since the salt contained in the waste fly ash washing liquid includes sodium chloride, potassium chloride, sodium carbonate, calcium chloride, etc., the composition is complex and the salt concentration is high, which makes the above units have low evaporation capacity and poor stability in actual operation. And problems such as poor salt discharge, so it is necessary to make innovative improvements to this unit.

Contents of the invention

In order to solve the problems existing in the prior art, the object of the present invention is to provide a garbage fly ash water washing liquid evaporation desalination system, and a method for evaporative desalination of the garbage fly ash water washing liquid using the system, thereby adapting to the garbage fly ash water washing The characteristics of complex liquid composition and high salt concentration ensure large-scale and stable disposal of garbage fly ash washing liquid.

In order to achieve the above object, the present invention adopts the following technical solutions:

An evaporative desalination system for garbage fly ash washing liquid, including a preheater, a falling film evaporator, a falling film separator, a forced circulation separator, a forced circulation evaporator, a thickener, a centrifuge, a mother liquor tank, a compressor system and Condensate water tank, in which, a feed pump is installed before the refrigerant inlet of the preheater, and the refrigerant outlet of the preheater is connected with the inlet of the falling film evaporator; the outlet of the falling film evaporator is connected with the inlet of the falling film separator; The separator is equipped with two liquid outlets, one of which is connected to the feed port of the falling film evaporator through a circulation pump, and the other liquid outlet is connected to the liquid inlet of the forced circulation separator through a material transfer pump; the forced circulation separator is equipped with three One liquid inlet and two liquid outlets, one of which is connected to the outlet of the forced circulation evaporator, one of the liquid outlets is connected to the inlet of the forced circulation evaporator through a forced circulation pump, and the other liquid outlet is connected to the outlet of the forced circulation evaporator through a discharge pump The thickener inlet is connected, and the second liquid inlet is connected with the outlet of the mother liquor tank through the mother liquor pump; the overflow port of the thickener is connected with the first inlet of the mother liquor tank, and the feeding port of the thickener is connected with the feed port of the centrifuge; the centrifuge mother liquor The outlet is connected to the other inlet of the mother liquor tank; the steam outlet of the falling film separator and the forced circulation separator are connected to the steam inlet of the compressor system after being joined by a pipeline; the steam outlet of the compressor system is connected to the steam inlet of the forced circulation evaporator; the forced circulation evaporator The steam outlet is connected to the steam inlet of the falling film evaporator, the condensed water outlet of the forced circulation evaporator is connected to the first inlet of the condensed water tank, and the condensed water outlet of the falling film evaporator is connected to the other inlet of the condensed water tank; the outlet of the condensed water tank is connected to the condensed water pump Connect with the heat medium inlet of the preheater.

The preheater is a plate heat exchanger.

The upper part of the falling film evaporator is provided with a liquid distribution pan.

The centrifuge is a two-stage piston pusher centrifuge or a decanter centrifuge.

The forced circulation separator is a positive circulation tangential feed evaporator.

In order to achieve the above object, another technical solution adopted by the present invention is:

A method for evaporating and desalting garbage fly ash water washing liquid, comprising the steps of:

1) Pump the pretreated garbage fly ash water washing solution into the preheater for heating, and the heating medium is condensed water after heat exchange;

2) After preheating, the material enters the falling film evaporator for evaporation and concentration, and the evaporation temperature in the falling film evaporator is controlled to be 103-107°C;

3) Evaporated and concentrated materials that are close to saturation enter the falling film separator for gas-liquid separation. After separation, the steam enters the compressor system. After separation, part of the liquid returns to the falling film evaporator through the pump to continue evaporation, and the other part of the liquid is injected into the forced circulation by the pump. Splitter;

4) The material in the forced circulation separator is subjected to deep evaporation and concentration through an external forced circulation evaporator, and the temperature of the liquid phase in the forced circulation separator is controlled to be 108-112°C;

5) After the material in the forced circulation separator reaches saturation or supersaturation, the gas-liquid separation is rapid. After separation, the steam enters the compressor system. After separation, the liquid has small particles of crystalline salt precipitated, and the crystalline salt falls to the bottom of the forced circulation separator and is pumped. into the thickener;

6) After the material containing crystalline salt settles in the thickener, the supernatant overflows to the mother liquor tank, and the concentrated material enters the centrifuge for separation to obtain crystalline salt, while the centrifuged mother liquor enters the mother liquor tank, and the mother liquor tank material is pumped into forced circulation Continue to evaporate and concentrate in the separator;

7) After the steam entering the compressor system is pressurized and heated to 116-118°C, it enters the forced circulation evaporator and falling film evaporator to heat the material, and the condensed water after heat exchange enters the condensed water tank and is pumped to the preheater The garbage fly ash washing solution is heated.

Further, the garbage fly ash washing liquid is heated for the second time after being heated by the preheater.

Further, the heating medium for the second heating is raw steam, and the heating method is heating by a plate heat exchanger.

Further, the volume solid-liquid ratio of the material containing crystalline salt is ≥30% after being settled by the thickener.

Further, after being pressurized and heated, the steam first enters the forced circulation evaporator and then enters the falling film evaporator to heat the material.

In order to adapt to the characteristics of complex components and high salt concentration of garbage fly ash washing liquid, the present invention divides evaporation concentration and evaporation crystallization into two relatively independent units, and utilizes MVR evaporation technology, and the heat energy is provided by the compressor system and maintained in balance; evaporation concentration The unit includes a preheater, a falling film evaporator and a falling film separator. Through preheating and repeated evaporation of the garbage fly ash washing liquid, the material is concentrated but not saturated; the evaporation crystallization unit includes a forced circulation separator, a forced circulation Evaporator, after the evaporative and concentrated material is further evaporated through this unit, the material reaches a saturated or supersaturated state, and the crystalline salt begins to precipitate; in the present invention, a thickener and a centrifuge are set up to further settle and concentrate the material containing the crystalline salt to achieve centrifugation. After separation requirements, after being effectively separated by a centrifuge, the crystallized salts are finally discharged out of the system.

The beneficial effects of the present invention are: (1) adopt falling film evaporator and forced circulation evaporator to evaporate and concentrate the material, adapt to the material property of waste fly ash washing liquid, and have the characteristics of more remarkable energy saving effect; (2) The fly ash washing liquid has gone through the steps of preheating, evaporation and deep evaporation, and the evaporation capacity is large, and the system operation is very stable; (3) The thickener and centrifuge are used to separate the crystallized salt, with high separation efficiency and smooth salt discharge; ( 4) It has good adaptability to the characteristics of large fluctuations in the salt concentration of the garbage fly ash washing liquid, and the adaptable range of the salt concentration can be 0-10%; (5) The invention is highly innovative and has good operational flexibility, Equipment working flexibility and long-term stability

Description of drawings

Figure 1 is a block diagram of the process flow of the waste fly ash water washing liquid evaporation desalination system.

In the figure: 1-preheater; 2-falling film evaporator; 3-falling film separator; 4-forced circulation separator; 5-forced circulation evaporator; 6-thickener; 7-centrifuge; 8- Mother liquor tank; 9-compressor system; 10-condensate water tank.

Detailed ways

One of the technical proposals of the present invention is an evaporative desalination system for garbage fly ash washing liquid, which will be described in detail below with reference to the accompanying drawings.

As shown in Figure 1, an evaporation and desalination system for garbage fly ash washing liquid includes a preheater 1, a falling film evaporator 2, a falling film separator 3, a forced circulation separator 4, a forced circulation evaporator 5, and a thickener 6. Centrifuge 7, mother liquid tank 8, compressor system 9 and condensed water tank 10.

In the above system, a feed pump is installed before the refrigerant inlet of the preheater 1, and the garbage fly ash washing liquid after decalcification and other treatments is pumped into the condensed water through the feed pump to exchange heat with the condensed water. The feed port of the evaporator 2 is connected, and the upper part of the falling film evaporator 2 is equipped with a liquid distribution plate. Through the dispersing effect of the liquid distribution plate, the garbage fly ash washing liquid enters the tube-side tubes of the falling film evaporator 2 evenly, from top to bottom Slowly flowing downwards, the heat exchange with the shell-side steam of the falling film evaporator 2 reaches the boiling point and forms an evaporation state.

The outlet of the falling film evaporator 2 is connected to the inlet of the falling film separator 3, and after being evaporated by the falling film evaporator 2, the material enters the falling film separator 3 for gas-liquid separation. The falling film separator 3 is provided with two liquid outlets. One liquid outlet is connected to the feed port of the falling film evaporator 2 through a circulation pump, so that the material is repeatedly evaporated in the falling film evaporator 2, and the other liquid outlet is connected to the liquid inlet of the forced circulation separator 4 through a transfer pump, so that the After gas-liquid separation, the high-concentration liquid turns to the crystallization unit.

The forced circulation separator 4 is provided with three liquid inlets and two liquid outlets, wherein one of the liquid inlets is connected with the forced circulation evaporator 5 outlets, and one of the liquid outlets is connected with the forced circulation evaporator 5 feed ports through the forced circulation pump, The other liquid outlet is connected to the thickener 6 inlet through the discharge pump, and the second liquid inlet is connected to the mother liquor tank 8 outlet through the mother liquor pump; the forced circulation separator 4 is a very important equipment of the crystallization unit, and the waste fly ash washing liquid is concentrated The liquid is further evaporated in the forced circulation evaporator 5, and reaches saturation or supersaturation in the forced circulation separator 4, so that the crystalline salt is precipitated.

The overflow port of the thickener 6 is connected to the inlet of the mother liquor tank 8, and the feed port of the thickener 6 is connected to the feed inlet of the centrifuge 7; the mother liquor outlet of the centrifuge 7 is connected to the other inlet of the mother liquor tank 8; the material containing crystallized salt After the thickener 6 settles, the supernatant of the thickener 6 enters the mother liquor tank 8, and after the solid-liquid ratio of the concentrated liquid at the bottom reaches 30%, it enters a two-stage piston pusher centrifuge or a decanter centrifuge for solid-liquid Separation, thereby obtained crystalline salt, and centrifugal separation mother liquor enters mother liquor tank 8 and returns to forced circulation separator 4 together with thickener 6 supernatant and evaporates again.

The steam outlet of the falling film separator 3 and the forced circulation separator 4 are connected to the steam inlet of the compressor system 9 after being merged through the pipeline, and the temperature of the steam is raised through the pressurization and temperature raising of the compressor system 9 to meet the requirements of evaporation and heat exchange; The steam outlet of the machine system 9 is connected to the steam inlet of the forced circulation evaporator 5; the steam outlet of the forced circulation evaporator 5 is connected to the steam inlet of the falling film evaporator 2, and the condensed water outlet of the forced circulation evaporator 5 is connected to the inlet of the condensed water tank 10, The condensed water outlet of the falling film evaporator 2 is connected to the other inlet of the condensed water tank 10, that is, the high-temperature condensed water after the heat exchange between the forced circulation evaporator 5 and the falling film evaporator 2 enters the condensed water tank 10; the outlet of the condensed water tank 10 passes through The condensed water pump is connected to the heat medium inlet of the preheater 1, and the heat exchanged through the preheater 1 reduces the temperature of the condensed water to about 40°C.

The preheater 1 is a plate heat exchanger, which has the characteristics of fast heat exchange speed and high heat exchange efficiency.

The forced circulation separator 4 is a positive circulation tangentially fed evaporator, which is conducive to the precipitation and increase of crystalline salts, and meets the requirements of subsequent centrifugal desalination.

Another technical solution of the present invention is a method for evaporative desalination of rubbish fly ash washing liquid, which will be described in detail through examples below.

Example 1

A method for evaporating and desalting garbage fly ash water washing liquid, comprising the steps of:

1) Turn on the feed pump, inject the pretreated garbage fly ash washing solution with a salt concentration of 8% into the preheater for heating, the heating medium is condensed water after heat exchange, and control the material temperature after heating to ≥95° ;

2) After preheating, the material enters the falling film evaporator for evaporation and concentration, and the evaporation temperature in the falling film evaporator is controlled to be 103-104°C;

3) After evaporation and concentration, the material with a salt concentration of 20-27% enters the falling film separator for gas-liquid separation. After separation, the steam enters the compressor system. After separation, part of the liquid returns to the falling film evaporator through the circulating pump to continue evaporation, and the other part It is pumped into the forced circulation separator by the material transfer pump;

4) The material in the forced circulation separator is subjected to deep evaporation and concentration through an external forced circulation evaporator, and the temperature of the liquid phase in the forced circulation separator is controlled to be 108-109°C;

5) After the material in the forced circulation separator reaches saturation or supersaturation, the gas-liquid separation is rapid. After separation, the steam enters the compressor system. After separation, the liquid has small particles of crystallized salt. pumped into the thickener;

6) After the material containing crystalline salt settles in the thickener, control the volume solid-liquid ratio of the concentrated material to ≥ 30%, the supernatant overflows to the mother liquor tank, and the concentrated material enters the centrifuge for separation to obtain crystallized salt, and the centrifuged mother liquor enters the mother liquor Tank, the mother liquor tank material is pumped into the forced circulation separator by the mother liquor pump to continue to evaporate and concentrate;

7) After the steam entering the compressor system is pressurized and heated to 116°C, it first enters the forced circulation evaporator and then enters the falling film evaporator to heat the material. The condensed water after heat exchange enters the condensed water tank and is pumped to the preheating The device heats the garbage fly ash washing liquid.

Example 2

A method for evaporating and desalting garbage fly ash water washing liquid, comprising the steps of:

1) Turn on the feed pump, inject the pretreated garbage fly ash washing solution with a salt concentration of 10% into the preheater for heating, the heating medium is condensed water after heat exchange, and control the material temperature after heating to ≥95° ;

2) After preheating, the material enters the falling film evaporator for evaporation and concentration, and the evaporation temperature in the falling film evaporator is controlled at 105-106°C;

3) After evaporation and concentration, the material with a salt concentration of 20-27% enters the falling film separator for gas-liquid separation. After separation, the steam enters the compressor system. After separation, part of the liquid returns to the falling film evaporator through the circulating pump to continue evaporation, and the other part It is pumped into the forced circulation separator by the material transfer pump;

4) The material in the forced circulation separator is subjected to deep evaporation and concentration through an external forced circulation evaporator, and the temperature of the liquid phase in the forced circulation separator is controlled to be 110-111°C;

5) After the material in the forced circulation separator reaches saturation or supersaturation, the gas-liquid separation is rapid. After separation, the steam enters the compressor system. After separation, the liquid has small particles of crystallized salt. pumped into the thickener;

6) After the material containing crystalline salt settles in the thickener, control the volume solid-liquid ratio of the concentrated material to ≥ 40%, the supernatant overflows to the mother liquor tank, and the concentrated material enters the centrifuge for separation to obtain crystallized salt, and the centrifuged mother liquor enters the mother liquor Tank, the mother liquor tank material is pumped into the forced circulation separator by the mother liquor pump to continue to evaporate and concentrate;

7) After the steam entering the compressor system is pressurized and heated to 117°C, it first enters the forced circulation evaporator and then enters the falling film evaporator to heat the material. The condensed water after heat exchange enters the condensed water tank and is pumped to the preheating The device heats the garbage fly ash washing liquid.

Claims (10)

1. A garbage fly ash water washing liquid evaporation desalination system is characterized in that: the system includes a preheater, a falling film evaporator, a falling film separator, a forced circulation separator, a forced circulation evaporator, a thickener, a centrifuge , mother liquid tank, compressor system and condensed water tank, wherein, a feed pump is installed before the refrigerant inlet of the preheater, and the refrigerant outlet of the preheater is connected with the inlet of the falling film evaporator; the outlet of the falling film evaporator is connected with the falling film evaporator The membrane separator is connected to the inlet; the falling film separator has two liquid outlets, one of which is connected to the feed port of the falling film evaporator through a circulation pump, and the other liquid outlet is connected to the forced circulation separator through a transfer pump and a liquid inlet Connection; the forced circulation separator is provided with three liquid inlets and two liquid outlets, one of which is connected to the outlet of the forced circulation evaporator, one of the liquid outlets is connected to the feed port of the forced circulation evaporator through a forced circulation pump, and the other One liquid outlet is connected to the thickener inlet through the discharge pump, and the second liquid inlet is connected to the outlet of the mother liquor tank through the mother liquor pump; the overflow port of the thickener is connected to the first inlet of the mother liquor tank, and the discharge port of the thickener is connected to the centrifuge The feed port is connected; the mother liquid outlet of the centrifuge is connected to another inlet of the mother liquid tank; the falling film separator and the forced circulation separator steam outlet are connected to the compressor system steam inlet after being merged through the pipeline; the compressor system steam outlet is connected to the forced circulation evaporator Steam inlet connection; the steam outlet of the forced circulation evaporator is connected to the steam inlet of the falling film evaporator, the condensate outlet of the forced circulation evaporator is connected to the first inlet of the condensate tank, and the condensate outlet of the falling film evaporator is connected to the other inlet of the condensate tank ; The outlet of the condensate water tank is connected with the heat medium inlet of the preheater through the condensate water pump. 2. The evaporative desalination system for garbage fly ash washing liquid according to claim 1, characterized in that: the preheater is a plate heat exchanger. 3. The waste fly ash water washing liquid evaporation desalination system according to claim 1, characterized in that: the upper part of the falling film evaporator is provided with a liquid distribution pan. 4. An evaporative desalination system for garbage fly ash water washing liquid according to claim 1, characterized in that: the centrifuge is a two-stage piston pusher centrifuge or a decanter centrifuge. 5. An evaporative desalination system for garbage fly ash washing liquid according to claim 1 or 2 or 3 or 4, characterized in that: the forced circulation separator is a positive circulation tangential feed evaporator. 6. A method for evaporating and desalting garbage fly ash washing liquid, characterized in that: the method comprises the steps of: 1) Pump the pretreated garbage fly ash washing solution into the preheater for heating, and the heating medium is condensed water after heat exchange; 2) After preheating, the material enters the falling film evaporator for evaporation and concentration, and the evaporation temperature in the falling film evaporator is controlled to be 103-107°C; 3) Evaporated and concentrated materials that are close to saturation enter the falling film separator for gas-liquid separation. After separation, the steam enters the compressor system. After separation, part of the liquid returns to the falling film evaporator through the pump to continue evaporation, and the other part of the liquid is injected into the forced circulation by the pump. Splitter; 4) The material in the forced circulation separator is subjected to deep evaporation and concentration through an external forced circulation evaporator, and the temperature of the liquid phase in the forced circulation separator is controlled to be 108-112°C; 5) After the material in the forced circulation separator reaches saturation or supersaturation, the gas-liquid separation is rapid. After separation, the steam enters the compressor system. After separation, the liquid has small particles of crystalline salt precipitated, and the crystalline salt falls to the bottom of the forced circulation separator and is pumped. into the thickener; 6) After the material containing crystalline salt settles in the thickener, the supernatant overflows to the mother liquor tank, and the concentrated material enters the centrifuge for separation to obtain crystalline salt, while the centrifuged mother liquor enters the mother liquor tank, and the mother liquor tank material is pumped into forced circulation Continue to evaporate and concentrate in the separator; 7) After the steam entering the compressor system is pressurized and heated to 116-118°C, it enters the forced circulation evaporator and falling film evaporator to heat the material, and the condensed water after heat exchange enters the condensed water tank and is pumped to the preheater The garbage fly ash washing solution is heated. 7. A method for evaporative desalination of garbage fly ash water washing liquid according to claim 6, characterized in that: the garbage fly ash water washing liquid is heated by a preheater and then heated for the second time. 8. A method for evaporative desalination of garbage fly ash washing liquid according to claim 7, characterized in that: the heating medium for the second heating is raw steam, and the heating method is heating by a plate heat exchanger. 9. A method for evaporative desalination of garbage fly ash washing liquid according to claim 6, characterized in that: the volume solid-liquid ratio of the material containing crystalline salt is ≥ 30% after settling through the thickener. 10. A method for evaporative desalination of garbage fly ash washing liquid according to any one of claims 6-9, characterized in that: after pressurized and heated, the steam first enters the forced circulation evaporator and then enters the falling film evaporator to heat the material .